Indium tin oxide semiconductor transparent conductive films (ITOs) are mainly used in, for example, thin-film field-effect transistor liquid crystal displays (TFT-LCDs), light-emitting diodes (LEDs), organic light-emitting diode (OLEDs), or the like. An etching liquid is required to be used for etching an ITO by a mask wet process to obtain a desired pattern.
An ITO etching liquid comprises an aqueous solution of hydrochloric acid and acetic acid, and a large amount of etching waste liquid, which exhibits to be acidic and contains a significant amount of hydrochloric acid and acetic acid, will be generated in the process of etching.
At present, a base, such as calcium hydroxide, calcium carbonate, or the like, is mainly used to perform neutralization treatment on an ITO etching waste liquid. However, this method not only wastes acid resources in the waste liquid, but also generates a large amount of waste water, which further results in environmental loads. At the meanwhile, indium, which is used as a raw material in the manufacture of an ITO target material, cannot be recovered. The rare metal indium is not only expensive, but also has a small storage amount. According to statistics, the global reserves of indium are merely 50 thousand tons, and those which can be exploited account for only 50% of the global reserves, and the consumption amount per year is 1700 tons or more. Therefore, the recovery and reutilization of indium is significantly meaningful to the protection of resources.